During
the past 10 years NASA's Hubble Space Telescope has pushed
back the frontier of virtually every area of astronomy. Hubble
has made dramatic contributions in understanding:

the atmospheres of planets

the birth, life, and death of stars

the properties of galaxies out to the farthest reaches of
the universe

supermassive black holes and their galactic hosts

the
abundance of light and heavy elements in the universe

the age of the universe

the fate of the cosmic expansion

Some
Hubble "firsts" include:

discovering that the sizes of galaxies are smaller in the
distant universe

sketching the cosmic star formation rate into the early
history of the universe

discovering young, massive star clusters formed in the collisions
of galaxies

identifying
absorbers of quasar light as galaxies

determining
accurate distances to variable stars in the Virgo cluster
of galaxies

imaging
the plume resulting from the impact of comet fragments on
Jupiter and of the "scars" at the impact sites

imaging
jets emanating from the center of an accretion disk around
a young star

At
the conclusion of Servicing Mission 4, scheduled for 2003,
astronomers will leave Hubble with the most powerful suite
of scientific instruments ever flown on the observatory.

During
Hubble's second decade, the science program will differ from
the present one in two important respects. In the second decade
the remaining two Great Observatories - the Chandra X-ray
Observatory and the Space Infrared Telescope Facility - will
be in full operation. The Next Generation Space Telescope
will be launced two years before Hubble's retirement. Coordinated
research campaigns involving all four of these extremely powerful
telescopes will be common.

It
is difficult to imagine a larger "quantum leap" in astronomy
than that provided by a view of the universe in which astronomers
will have simultaneous coverage from X-rays through optical
and near-infrared wavelengths to the deep infrared using this
fleet of major space telescopes.

Secondly,
special emphasis will be placed on large programs intended
to push Hubble to its limits and to address the most important
scientific questions that can be answered by the telescope
before its mission comes to an end. These are called "Treasury
Programs." Past examples of this approach include the Hubble
Deep Field, the Hubble Constant Key Project, and the comet
Shoemaker-Levy 9 impact on Jupiter. All of these programs
had a huge impact on science.